Process of making sulphates



' oxide gases of a.

Patented Feb.. 27, I923.

Mltttddti PATENT orrrcs.

HARRY PAULING, 01E BERLIN-GRUNEW, GEBIIIANY.

PROCESS OF MAKING- SULPHATES.

1J0 Drawing.

T 0 ct whom it may concern Be it known that I, HARRY PAULING, a citizenof the Stateof Prussia, Republic of Germany, residing atBerlin-Grunewald, Germany, have invented a new and useful Process ofMaking Sulphates (for which I have filed application in Germany onJanuary 27, 1920), of which the following is a specification.

In the manufacture of sulphates from metals which are readily soluble insulfuric acid, the practice hitherto, has been to subject the metals tothe action of sulfuric acid and oxygen. In carrying out a process ofthis kind, it has been usual to granulate the metals and to pour theminto tower-shaped receptacles into which sulfuric acid was sprayed fromabove, while a current of airand of hydrogen was driven upwards frombelow. The solution thus produced was repeatedly sent through the toweruntil it had reached the. predetermined degree of concentration and thesulfuric acid employed had been spent. This procedure, however, isobjectionable by reason of its excessive duration, as well as for thereason that an amount of air, by far exceeding the theoretical demand,had to be blown in, carrying along with it a correspondingamount ofhydrogen, and, finally, for the reason that large quantities of metalshas to be constantly kept in the towers, thereby causing a considerablefinancial loss if the metal to be treated is a costly one, such ascopper or nickel.

I am aware that it is known to add nitric acid to the sulfuric acidemployed to dissolve metals, for the purpose of accelerating the processof dissolution; the nitric acid, in such case, delivering or supplyingthe oxygen necessary to produce the sulphate, due to the fact that it isitself reduced to nitrous lower grade. This property of nitric acid,however, has not been employed in trade, as the reaction does not go tocompletion if thereis no considerable excess of sulfuric acid present.But even in the presence of a suficient excess of sulfuric acid theprocess of dissolut on, which is rather rapid in the beginning, proceedsslower and slower, so that in consequence of the heat required aconsiderable amount of heat must still be sup-plied, such amount beingfurther increased by the fact that the nitric oxides formed must beremoved from the solution by a blast of air. This fact and Now, oncoolin Application filed August 26, 1921. Serial No. 495,721.

the evaporation thereby caused require a considerable amount of heat;and. there is the further objection that the nitrous gases, owing to theconsiderable amount of water which they contain, cannot be regeneratedexcept to a very weak nitric acid; The latter is too dilute to be usedagain in the process, unless it be once more brought up to. the requiredconcentration, which would entail additional costs. Owing to all thesedim culties, the use of nitric acid for the purpose described above hasnot been adopted com.- mercially.

To do away with the objections above mentioned is the purpose of thepresent invention; and to attain such purpose, according to the improvedprocess, the nitric acid.

is first caused to act alone on the metal, the

said acid, if desired, being previously heated. Owing to such action,the change into the respective nitrate will, first, be effected. Butthis transformation will take place in a much shorter period of timethan would have been the case in the presence of sulfuric acid. As soonas the reaction begins to decrease, the nitrate solution is separatedfrom the metal in' excess, whether there is still some nitric acidpresent or not; and, after maxing said nitrate with the required amountof sulfuric acid, the blowing out with air is carried out in order toremove all nitric oxides which. may still be present. When the nitricacid, bound to the nitrate, has been replaced by sulfuric acid and thereby hasbecome free a mixture will be formed of a solution of sulphate anda strong nitric acid. The blast of air, accordingly, will not cause theescape of vapor of water and of nitrate gases, but the escape of strongnitric acid and nitric gases. Thus by the regeneration of the nitrategases the result will not be a diminution but an increase of strength inthe regenerated nitric acid.

sulphate will Wlll be eliminated, leaving a mother-liquor which consistsof strong nitric acid, in which only a sllight amount of sul-. phate andsome nitrate, besides traces of sulfuric acid, are contained. ,Thecrystals are then separated from the mother-liquor and washed in a knownmanner, after which they are dried and constitute the finished product.The said crystals, however, may be subjected to a further or renewedcrystallization, as a result of which crystals of a larger size will beformed.

down of the solution, the

v ea ers The advantages and novel technical :tea-- been stated above, anaddition of sulphuric tures of the described process, accordingly, acidwill cause a change into sulphate and consist in accelerating in a quiteextraordia corresponding-amount of nitric acid will nary manner theprocess of decomposition be set free. The nitric acid causes an intenseup to the point where the nitrate is formed, reduction of the solubilityof the copper 7o whereupon it is terminated without necessulphate Withinthe mother-liquor; and sitating that the entire quantity of nitricmoreover,v as the crystallization of each acid be transformed; furtherin that the enmolecule of copper sulphate deprives the haustion of thenitric acid need not be iolsolution of live molecules of water, it willto lowed up to the formation at the lowest beclear that the remainingnitric acid will 75 stage o t oxidation of the nitrogen, which possess ahigh degree of concentration. it would cause losses of nitrogenand,-consecontains, as has been mentioned before, only quently, ofnitricacid; and, finally, in that a small quantity of nitrate and ofsulphuric the nitric oxides may be regenerated to acid and is in a statetobe returned into a height fully suficient for the purposes the primarydecomposition receptacle. The of this process. The processofcrystallizawhole process of transformation of the given tion islikewise accelerated to an extraordiquantity of copper into sulphatewill take nary degree, whereby the size of the apparanot more than aboutan hour or less, whereas tus' required is considerably reduced.heretofore the same quantity could onlybe In the following T shalldescribe the procobtained within a period of from one-half ess asapplied, by way of example, to the to two months; that is, more thanthousand production of copper sulphate from metallic times longer. if itis desired to obtain copper. crystals of a larger size, the smallcrystals Within a receptacle made of stoneware or are subjected to asecond crystallizing op- 3 5 other acid-proof material, provided with aeration which may be performed in a known cover and an outlet, a certainquantity of manner. A special advantage derived from copper is depositedin a suitable form. This such renewedcrystallization consists in that vreceptacle, the cover of which has been the operation, which requireschambers of I closed, is then filled with nitric acid of a larger size,is performed with a neutral about 50%.strength to about one-third ofsolution, which produces perfectly pure crys- 95 itsheight. The saidnitric acid should only tals entirely free of any acid.

' .be heated to a moderate degree, as the teml fit is desired tomanufacture nickel sulperature will soon rise in consequence of thephate, attention should be given to the fact reaction. A rapid reactionwill at once he that the crystallization requires seven molegin,developing a great quantity of strong cules of water, so that theconcentration of 1 nitrous gases which are conducted to an ah the nitricacid and the sulfuric acid must be sorption chamber where they areregenev calculated accordingly. The same remarks rated into nitric acidof about 50% strength apply to the treatment of brass and other in aknown manner. When the rapid r alloys; the concentration of the acids tobe 0 generation of the gases starts to I decrees employed in every caseshould be calculated 1% which will take about half an hour withaccording to the amount of water required receptacle holding 600 liters,the acid ni for the crystallization of the final product.

5 -trate' solution, having a temperature of Care should be taken toavoid equally a about 70C., is led oil into another recepwant of waterandia surplus of water, and,

tacle, wherein it becomes mixed for a short further, attention should begiven to the fact HO time with a gradual addition of sulphuric that bythe final washing of the crystals acid, under compressionof air. The airsatsmall quantities of water will always enter urated with vapors ofnitric acid is likeinto the process. 1 a

wiseintroduced into the absorption chame ll claim:

her. Within the second receptacle the ni- 1. A process ofconvertingmetallic subno trate is transformed into sulphate, and on stances whichare insoluble or dificultly now cooling down the receptacle, either withsoluble in sulfuric acid into sulphates by water or by continuing, theair blast, the the utilization of nitric acid, comprising formation andseparation of crystals of copthe steps of causing concentrated nitric ersulphate will begin. The period of acid to act on the metallic substanceunder 12d lowing out and of crystallization will last treatment untilthe greater part of the ac d about 30minutes, during which time a fresh;has been bound by the action; separat ng charge of nitric acid will beacting on more the mrongly acidulated nitrate solutlon copper. Thecharge of copper should, of thereby formed from the metal in excess;

coursc,be completed by compensating for the mixing said nitrate solutionwith sulfuric amount consumed. The mixture of mother acid; subjectingthe resultant solution to liquor and of crystals is drawn ofi-either bycrystallization; separating the crystals from suction orby centrifugalforce, and the cryssaid resultant solution; and washing sald tals arefreed from the mother-liquor and crystals.

( 5 then washed in a lrnown manner. As has 2. A process of convertlngmetallic vsubltd naeaave stances which are insolublev or difiicultlysoluble in sulfuric acid into sulphates by the utilization of nitricacid, comprising the steps of causing concentrated nitric acid to act onthe metallic substance under treatment; separating the nitrate solutionthereby formed from the metal in excess; mixing said nitrate solutionwith sulphuric acid; subjecting the resultant solution to an air blastto remove all nitric oxides; cooling said resultant solution to causethe sulphate therein to crystallize out; separating the sulphatecrystals; and Washing said crystals. v

3. A process of converting metallic substances Which are insoluble ordithcultly soluble in sulfuric acid into sulphates by the utilization ofnitric acid, comprising" the steps of causing concentrated nitric acidto act on the metallic substance under treatment; separating the nitratesolution thereby formed from the metal in excess; mixing said nitratesolution with sulphuric acid; subjecting the resultant solution to anair blast to remove all nitric oxides; cooling said resultant solutionto cause the sulphate therein to crystallize out, leaving amother-liquor consisting substantially of strong nitric acid; separatingand Washing the sul hate crystals; and returning the mother-'iquor foruse on a fresh charge of metallic substance.

In testimony whereof I have affixed my signature HARRY PAULING.

